Adjustable CTE polymer compositions for extrusion and additive manufacturing processes

ABSTRACT

A polymer composition capable of being additively manufactured includes a polymer matrix and an NTE additive. The NTE additive enables tailoring of the CTE of the polymer composition and the additively manufactured structure made using the composition.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to and the benefit of U.S. ProvisionalPatent Application Ser. No. 62/882,425, filed Aug. 2, 2019, and titled“ADJUSTABLE CTE POLYMER COMPOSITIONS FOR EXTRUSION AND ADDITIVEMANUFACTURING PROCESSES,” and U.S. Provisional Patent Application Ser.No. 62/882,423, filed Aug. 2, 2019, and titled “POLYMER COMPOSITIONSCAPABLE OF INDUCTION HEATING FOR EXTRUSION AND ADDITIVE MANUFACTURINGPROCESSES,” the entire contents of all of which are incorporated hereinby reference.

BACKGROUND

Molds and cauls, among other structures, are commonly used to fabricatecomposite parts. These molds, cauls and other structures (also referredto herein as “tools”) are typically prepared from metallic or polymericmaterials. The polymeric materials often include modifications to thepolymers used to make the tools. These modifications are commonly madeto impart certain desired properties to the tools post-cure. Forexample, conventional polymeric materials for the production of thesetools have included the addition of certain additives to modify thecoefficient of thermal expansion (CTE), increase strength, and reducewarpage in the extruded polymers. These additives have conventionallybeen incorporated into the tools in fiber form, but polymer modificationusing fibers has certain limitations, and to date, no compositionsincorporating expansion controlling fillers have been developed that aresuitable for additive manufacturing and/or extrusion manufacturingprocesses for manufacturing the tools.

For tool manufacturing, one of the major problems with current additivemanufacturing techniques is the highly anisotropic behavior of thepolymers, and their lack of thermal conductivity. The highly anisotropicbehavior of the polymers used in additive manufacturing techniques is aprimary result of attempting to control the thermal expansion, strength,and warpage of the printed (i.e., additively manufactured) material (orstructure). The polymers used in these manufacturing techniques can bemodified by the addition of certain fibers to modify the coefficient ofthermal expansion (CTE), increase strength, and/or reduce warpage in theextruded or printed polymer. However, in additive manufacturingprocesses, the addition of fibers to the polymer printing compositionsresults in a printed bead that has different thermal expansionproperties in the print direction, across the bead width, and throughthe bead thickness due to the different orientations of the fiberswithin the polymer matrix. In fact, the inconsistent orientation of thefibers within the polymer matrix leads to significant dissimilarities ina wide variety of mechanical and thermal properties.

SUMMARY

According to embodiments of the present disclosure, a polymercomposition comprises a polymer matrix and a negative thermal expansion(NTE) additive, and the polymer composition is configured for additivemanufacturing or extrusion.

The NTE additive may comprises a powder or particulate having an averageparticle size of about 10 μm or smaller. In some embodiments, the NTEadditive comprises a material selected from transition metal tungstates,transition metal molybdates, zirconium vanadates, zeolites exhibitingNTE, aluminum phosphates exhibiting NTE, Prussian blue analogs,antiperovskite manganese nitrides, β-eucryptite, BiNi_(1−x)Fe_(x)O₃compounds in which x is less than 1 and greater than 0, Ca₂RuO_(4−γ),combinations thereof, hybrids thereof, and mixtures thereof. Forexample, in some embodiments, the NTE additive comprises one or moretransition metal tungstates, one or more antiperovskite manganesenitrides, β-eucryptite, a combination thereof, a hybrid thereof, or amixture thereof.

In some embodiments, the polymer composition may also include one ormore auxiliary additives. The one or more auxiliary additives maycomprise one or more strengtheners, one or more magnetically receptivematerials, or one or more colorants. The one or more strengtheners maycomprise a material selected from the group consisting of carbon fibers,glass fibers, aramid fibers, metal fibers, metal coated fibers, andcombinations thereof.

According to some embodiments, the NTE additive may be present in thepolymer composition in an amount of about 1 to about 60 vol % based on100 vol % of the polymer composition.

In some embodiments, a tool for use in manufacturing a composite partcomprises the polymer composition after additive manufacturing orextrusion. The tool may comprise the polymer composition after extrusionand have a constant cross-section. The tool may comprise the polymercomposition after additive manufacturing and have a net shape or desirednet shape.

According to some embodiments, a method of making a tool for use inmanufacturing a composite part comprises additively manufacturing orextruding the polymer composition.

In some embodiments, a method of making a composite part comprisesadditively manufacturing or extruding the polymer composition to form atool, applying a composite part composition or composite part laminateon or to the tool, and exposing the tool to sufficient heat to cure thecomposite part composition or composite part laminate.

According to some embodiments, a system for manufacturing a compositepart comprises a tool additively manufactured or extruded from thepolymer composition, a heating element, and a controller configured tocycle the heating element on and off. The system may further compriseone or more thermocouples in contact with or embedded in the tool, andin communication with the controller. The one or more thermocouples andthe controller may define a continuous feedback loop in which thecontroller receives temperature data regarding the temperature of thetool at regular intervals, and the controller automatically cycles theheater on and off in response to the temperature data when thetemperature of the tool reaches or exceeds a predetermined thresholdtemperature.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of embodiments of the present disclosurewill be better understood by reference to the following detaileddescription when considered in conjunction with the drawings, in which:

FIG. 1 is a schematic view of an extruder printing multiple layers of apolymer composition according to embodiments of the present disclosure;

FIG. 1A is an exploded out schematic view of the multiple layers of FIG.1 showing the distribution of various additives and fillers in thepolymer composition according to embodiments of the present disclosure;and

FIG. 2 is a schematic diagram of a system for manufacturing a compositepart, according to embodiments of the present disclosure.

DETAILED DESCRIPTION

According to embodiments of the present disclosure, a polymercomposition is useful for extrusion and additive manufacturing processesto produce tools satisfying the demands of the composite industry. Insome embodiments, the polymer composition comprises a polymer matrix anda negative thermal expansion (NTE) additive. In some embodiments, forexample, the polymer composition comprises the polymer matrix filled(e.g., uniformly filled) with the NTE additive. The NTE material may beincorporated (or dispersed) into the polymer matrix as particles orfibers (e.g., short fibers). Additionally, the dispersion (e.g., uniformdispersion) of the NTE additive in the polymer matrix prior tomanufacture effectively negates (or reduces or significantly reduces)the anisotropic behavior of the composition since the NTE materials aredispersed in the polymer composition prior to additive manufacture orextrusion, resulting in a printed (or extruded) product havingwell-integrated NTE materials. This reduces (or significantly reduces oreliminates) the discrepancies in thermal expansion properties of theprinted bead, resulting in polymer compositions uniquely suited forprinting tools (e.g., meeting the standards required in the compositeindustry) using additive manufacturing or extrusion techniques.Additionally, as the NTE additive contracts upon exposure to heat (i.e.,the NTE additive has a negative coefficient of thermal expansion (CTE))while the polymer in the polymer composition expands (i.e., the polymerhas a positive CTE), addition of the NTE additive to the polymercomposition can reduce or negate expansion of the manufactured tool uponexposure to heat. Indeed, the NTE additive can either reduce theexpansion (i.e., the CTE) to acceptable levels, negate the expansionaltogether (e.g., produce a net-zero expansion), or even push theexpansion to negative levels (i.e., produce a composition as a wholethat has a negative CTE such that it contracts rather than expands onexposure to heat). This ability to tailor the thermal expansionproperties (e.g., the CTE) of the manufactured tool enables themanufacturing of tools CTE-matched to the composite part fabricatedusing the tool.

As noted generally above, according to embodiments of the presentdisclosure, a polymer composition useful for the extrusion or additivemanufacturing of composite tools (e.g., molds, cauls, etc.) includes apolymer matrix and an NTE additive. The polymer of the polymer matrix isnot particularly limited, and may be any polymer suitable for use inextrusion and additive manufacturing techniques and processes, andsimilar or equivalent processes and techniques. Indeed, those ofordinary skill in the art would be capable of selecting an appropriatepolymer for the polymer matrix based on the desired structure andproperties of the resulting additively manufactured or extruded tool.Some nonlimiting examples of suitable polymers for the polymer matrixinclude fluoropolymers, ethylene-vinyl acetate (EVM) polymers,silicones, elastomers (including but not limited to thermoplasticelastomers), thermoset polymers or plastics, and thermoplastic polymersor plastics. Nonlimiting examples of suitable thermoset polymers andplastics include urethanes, vinyl esters, epoxies, bismaleimides (BMI),benzoxazines, cyanates, phenolics, and the like, including mixturesthereof, derivatives thereof, and co-polymers of two or more thereof.Nonlimiting examples of suitable thermoplastic elastomers, polymers orplastics include acrylonitrile butadiene styrene (ABS) polymer systems,polyphenylene sulfide (PPS) polymer systems, polyphenylsulfone (PPSU)polymer systems, polyetherketone (PEK) polymer systems,polyetheretherketone (PEEK) polymer systems, polyaryletherketone (PAEK)polymer systems, polyethersulfone (PES or PESU) polymer systems,polycarbonate (PC) polymer systems, polylactic acid (PLA) polymersystems, polyvinyl alcohol (PVA) polymer systems, and the like,including mixtures thereof, derivatives thereof, and co-polymers of twoor more thereof.

As would be understood by those of ordinary skill in the art, thepolymer matrices discussed above may be prepared in any suitable manner,using any suitable reactions and reactants. For example, in someembodiments, the polymer matrices may be thermally cured by mixing theappropriate monomers and exposing the mixture to heat sufficient toeffect curing. In some embodiments, however, the polymer matrices may bechemically cured, e.g., by mixing the appropriate monomers with ahardener (or curing agent), and allowing the monomers and hardener (orcuring agent) to react for a sufficient amount of time to effectcross-linking and/or curing. Suitable hardeners (or curing agents) arewell known to those of ordinary skill in art, and may differ dependingon the polymer matrix being prepared. Those of ordinary skill in the artwould be capable of selecting an appropriate hardener (or curing agent)based on the polymer species being used to prepare the polymer matrix.The chemical curing mechanism may be particularly suitable for preparingthermoset polymer systems. In some embodiments, the polymer matrices maybe prepared using a combination of thermal and chemical curingmechanisms. Also, any other known or suitable curing techniques may beused to prepare the polymer matrices, including but not limited toelectron beam, ultraviolet (UV) radiation, X-ray and microwaveprocesses.

The NTE additive is also not particularly limited, and may be anymaterial that itself either contracts (rather than expands) uponexposure to heat (e.g., has a negative coefficient of thermal expansion(CTE)), or itself has zero or near zero thermal expansion. Indeed, asused herein, the term “negative thermal expansion additive” or “NTEadditive” refers to any material that is capable of reducing the thermalexpansion properties of the polymer composition, and includes thosematerials that reduce the thermal expansion to acceptable levels, negatethe thermal expansion altogether (e.g., yield a polymer composition withnet-zero thermal expansion, or bring the thermal expansion to negativelevels (e.g., yield a polymer composition with negative thermalexpansion such that the composition as a whole contracts on exposure toheat). With that in mind, those of ordinary skill in the art would becapable of selecting an appropriate material for the NTE additive basedon the polymer in the polymer composition, and on the desired thermalexpansion properties of the resulting composite tool (e.g., the desireddegree of thermal expansion reduction).

Any suitable material with NTE properties may be used for the NTEadditive, without limitation, and many materials with this property areknown and commercially available. Any now known or hereafter developedor discovered materials with NTE properties may be used as the NTEadditive, including any and all commercially available such products nowor hereafter available. Some nonlimiting examples of suitable materialsfor the NTE include: transition metal tungstates (including, forexample, zirconium tungstates (e.g., ZrW₂O₈), scandium tungstates (e.g.,Sc₂W₃O₁₂), hafnium tungstates (e.g., HfW₂O₈), etc.)); transition metalmolybdates (e.g., zirconium molybdates (e.g., ZrMo₂O₈), scandiummolybdates (e.g., Sc₂Mo₃O₁₂), hafnium molybdates (e.g., HfMo₂O₈),etc.)); zirconium vanadates (e.g., ZrV₂O₇); zeolites (i.e., thoseexhibiting NTE); aluminum phosphates (i.e., those exhibiting NTE);Prussian blue analogs (including but not limited to transition metals,semiconductors and/or precious metal analogs of Prussian blue, includingbut not limited to Zn, Mn, Co, Ni, Cu, Cd, Fe, Ga, Pt, Sc and Hf analogsof Prussian blue, including, for example, Zn₃[Fe(CN)₆], Fe[Fe(CN)₆],Fe₃[Co(CN)₆], Ga[Fe(CN)₆], M[Pt(CN)₆] where M is Mn, Fe, Co, Ni, Cu, Zn,Cd, etc., and others); antiperovskite manganese nitrides (including butnot limited to those with the structure Mn₃MN in which M is a dopant,such as but not limited to one or more transition metals, semiconductorsand/or precious metals, e.g., Pt, Ag, Au, Sn, Cr, Zn, Ge, Cu, Ga, Fe,Ni, Co, Cu, Cd, Fe, Sc, Hf, etc.); β-eucryptite; BiNi_(1−x)Fe_(x)O₃compounds in which x is less than 1 and greater than 0; Ca₂RuO_(4−γ);combinations thereof, hybrids thereof, and mixtures thereof. Someadditional nonlimiting examples of suitable NTE materials are describedin U.S. Patent Publication No. 2007/0135550 to Chakrapani et al., titled“NEGATIVE THERMAL EXPANSION FILLER FOR LOW CTE COMPOSITES,” and filed onDec. 14, 2005, the entire contents of which are incorporated herein byreference. As noted above, the NTE additive is not limited to the listedmaterials (which are not intended to constitute an exhaustive list), andthe transition metals in these species can be substituted, and hybridspecies can be sintered using spark plasma sintering or other similarsintering processes. Indeed, NTE materials are the subject of constantand ongoing research, and new NTE species are being and will bediscovered and developed in the future. The NTE additive according toembodiments of the present disclosure encompasses all NTE materials thatare now known (including those listed above and others that arecurrently known) as well as those equivalents that are yet to bedeveloped.

Additionally, the NTE additive may include a coated NTE additive inwhich an NTE material is coated with a coating material (which may nothave NTE properties) to increase the additive's performance and/oreffective bond strength in the polymer matrix. In these embodiments, thecoating material is not particularly limited and may be any coatingmaterial capable of incorporation into the polymer composition (orresulting tool, as discussed further below). Some nonlimiting examplesof suitable coating materials (for coating the NTE material) include anypolymer compatible with the polymer matrix material, such as but notlimited to polymethylpentene (PMP).

As noted above, these lists of NTE additives, coated NTE additives andcoating materials are not exclusive, and as new NTE materials aredeveloped and made available commercially, those materials are alsointended to be covered by the terms “negative thermal expansionadditives” or “NTE additives” or as equivalents thereof under theDoctrine of Equivalents.

In embodiments of the present disclosure, the NTE material (whether acoated additive or not) may be added, mixed, dispersed or otherwiseincorporated into the polymer matrix or included in the polymercomposition in any suitable form, for example powder (or particulate)form or fiber (e.g., short fiber) form. While the particle size of thepowder (or particulate) and length of the fibers are not particularlylimited, in some embodiments, the powder (or particulate) may have anaverage particle size (and the fibers may have an average fiber length)of about 50 μm or smaller, for example about 30 microns or smaller, orabout 20 microns or smaller. And in some embodiments, the powder (orparticulate) may have an average particle size (and the fibers may havean average length) of about 10 μm or smaller, for example, 7 μm orsmaller, 5 μm or smaller, or about 3 μm to about 5 μm. Additionally, thelower limit of the particle size (or fiber length) is not particularlylimited. However, in some embodiments, the powder (or particulate) mayhave an average particle size (and the fibers may have an averagelength) of about 1 μm or greater, e.g., about 1 μm to about 50 μm, about1 μm to about 30 microns, about 1 μm to about 20 microns, about 1 μm toabout 10 μm, about 1 μm to about 7 μm, or about 1 μm to about 5 μm.

In some embodiments in which the NTE additive is included in the polymercomposition in fiber (or short fiber) form, the fibers may have thelengths discussed above. However, in some embodiments, the fibers may belonger, for example, 10 mm or shorter, for example 5 mm or shorter, or 3mm or shorter. Indeed, the length of the fibers (or short fibers) is notparticularly limited as long as the fibers can be effectivelyincorporated into the polymer composition, and as long as the resultingpolymer composition can be used in additive manufacturing or extrusiontechniques. Additionally, when the NTE additive is included in thepolymer composition as fibers, the fibers may be damaged during theextrusion or additive manufacturing process. Accordingly, the fibersexisting in the manufactured tool (resulting from the additivemanufacturing or extrusion (and curing) of the polymer composition) mayhave average lengths (or short dimensions) that are shorter than theaverage lengths of the fibers mixed or compounded in the polymercomposition prior to the additive manufacturing or extrusion process.The individual fibers may be damaged differently during themanufacturing process, and the damage to the fibers may differ from runto run in the manufacturing process, and may differ in differentmanufacturing processes (e.g., the damage caused during extrusion may bedifferent than the damage caused during additive manufacturing). Assuch, the average length of the fibers in the manufactured tool maydiffer depending on the additive manufacturing or extrusion processemployed to make the tool, the conditions of the manufacturing process,and the composition of the fibers and the polymer composition. In someembodiments, however, the fibers in the manufactured tool may have anaverage length (or long dimension) of about 5 mm or shorter, forexample, about 2.5 mm or shorter, or about 1.5 mm or shorter.

As used herein, the terms “fiber” and “short fiber” denote an elongatedstructure in which a length (or long) dimension is larger (or longer)than a width (or short) dimension. As such, while the length (or longdimension) of the fibers may fall within the ranges discussed above, thewidth (or short dimension) of the fibers may be shorter (orsignificantly shorter) than the length. By incorporating the NTEmaterial into the polymer matrix in particulate or fiber (or shortfiber) form, the smaller dimensions of the particles or fibers of theNTE additive particles enable negation (or reduction/minimization) ofthe anisotropic behavior of the manufactured tool.

The amount, ratio and/or proportions of the polymer matrix and the NTEadditive are not particularly limited, and may have any value so long asthe resulting polymer composition remains suitable for the intendedmanufacturing process (e.g., extrusion or additive manufacturing) andcapable of use in the fabrication of composite parts. Indeed, in someembodiments, the amount, ratio and/or proportions of the polymer matrixand NTE additive are tailored or selected to achieve the desired ortarget expansion properties in the manufactured tool. Indeed, theamount, ratio and/proportions of the polymer matrix and the NTE additive(as well as the selection of the NTE additive material) may differdepending on the polymer selected for the polymer matrix (and thatpolymer's thermal expansion properties), the desired thermal expansionproperties of the manufactured tool (e.g., negative thermal expansionsuch that the tool contracts within acceptable tolerances upon exposureto heat, net-zero thermal expansion such that the tool neither expandsnor contracts upon exposure to heat, or positive (but reduced) thermalexpansion such that the tool expands within acceptable tolerances uponexposure to heat), and the thermal expansion properties of the compositepart intended to be fabricated using the tool.

Accordingly, in some embodiments, the amount, ratio and/or proportionsof the polymer matrix and the NTE additive may be used to tailor thepolymer compositions for different purposes or materials. For instance,the amount, ratio and/or proportions of the polymer matrix and the NTEadditive may differ depending on the type of polymer and NTE additiveused in the polymer composition. As such, different combinations ofpolymers and NTE additives may have different amounts, ratios and/orproportions of the polymer and NTE additive in order to achieve thedesired properties in the resulting printed or extruded tool. Forexample, certain polymers (e.g., polyphenylene sulfides) may requirelarger amounts of NTE additive in order to meaningfully affect thethermal expansion properties of the polymer composition, and the amountsof NTE additive needed for amorphous materials is lower (orsignificantly lower) than that the amounts needed for semi-crystallinematerials). Indeed, the amount, proportions and/or ratios of the NTEadditive and polymer may be selected or tailored to match the CTE of themanufactured tool to the CTE of the composite part intended to befabricated using the tool. As different composite parts may havedifferent compositions and different CTEs (e.g., carbon fiber reinforcedcomposites typically have a CTE of 2 to 3 ppm/C, glass reinforcedcomposites typically have a CTE of 10-14 ppm/C, and aramid reinforcedcomposites typically have a CTE of 6 to 8 ppm/C), such CTE-matching canensure that any expansion upon exposure to heat is consistent within thetool and the composite part being fabricated using the tool.

In some embodiments, for example, the polymer matrix may be present inthe polymer composition in an amount of about 40 to about 99 vol %(based on the total volume of the polymer composition), for example,about 40 to about 94 vol % (based on the total volume of the polymercomposition). And the NTE additive may be present in the polymercomposition in an amount of about 1 to about 60 vol % (based on thetotal volume of the polymer composition), for example, about 1 to about30 vol % (based on the total volume of the polymer composition), orabout 1 to about 15 vol % (based on the total volume of the polymercomposition).

In addition to the polymer matrix and the NTE additive, in someembodiments, the polymer composition may further include a variety ofdifferent auxiliary additives. The auxiliary additives are notparticularly limited, and may include any materials capable of modifyinga desired or selected property of the polymer composition (andconsequently, a desired or selected property of the tool resulting fromthe additive manufacturing or extrusion process). Some nonlimitingexamples of suitable such auxiliary additives include strengtheners,magnetically receptive materials, and colorants. The strengtheners maybe any suitable material capable of enhancing the mechanical strength ofthe additively manufactured or extruded tool. Nonlimiting examples ofsuitable strengtheners include fibers, such as, but not limited tocarbon fibers, glass fibers, aramid fibers, metal fibers and metalcoated fibers (e.g., metal coated carbon, glass or aramid fibers). Thesefibers may have any suitable shape and/or size, including an averagelength dimension similar to that of the fibers discussed above inconnection with the NTE additive. When included in the polymercomposition, a single type of strengthener may be used, or a combinationof two or more different types of strengtheners may be used, withoutlimitation. Also, the amount of the strengthener(s) in the polymercomposition is not particularly limited, and may be any amount suitableto achieve the desired strengthening effect. As the desired strength ofthe additively manufactured or extruded tool may differ depending on theintended application of the tool, the amount of the strengthener may betailored or selected based on the intended application of the tool. Andthose of ordinary skill in the art would be capable of selecting anappropriate amount of the strengthener in the polymer composition basedon the intended application of the manufactured tool and the desiredstrength of that tool for the intended application. In some embodiments,for example, the strengthener (such as, but not limited to, carbonfibers) may be included in the polymer composition in an amount of about1 to about 30 vol % (based on the total volume of the polymercomposition), for example, about 5 to about 30 vol % (based on the totalvolume of the polymer composition), about 1 to about 20 vol % (based onthe total volume of the polymer composition), or about 5 to about 20 vol% (based on the total volume of the polymer composition).

Additionally, in some embodiments, the strengtheners discussed above mayalso serve as secondary thermal expansion modifiers. For example, inembodiments including carbon fibers as a strengthener, the carbon fibersmay also have an effect on the thermal expansion properties of thepolymer composition (e.g., on the coefficient of thermal expansion(CTE)), and of the additively manufactured or extruded tool. As thedesired thermal expansion properties (and thus the amount or degree ofmodification needed or desired) of the additively manufactured orextruded tool may differ depending on the intended application of thetool (as discussed above), the amount of the strengtheners (e.g., thosedoubling as a secondary thermal expansion modifier) may be tailored orselected based on the intended application of the tool, and on theselected NTE additive and amount of that additive. And those of ordinaryskill in the art would be capable of selecting an appropriate amount ofthe strengthener (e.g., one doubling as a secondary thermal expansionmodifier) in the polymer composition based on the intended applicationof the manufactured tool, the desired thermal expansion properties ofthat tool (e.g., positive, net-zero, or negative expansion) for theintended application, and on the composition and amount of the NTEadditive in the polymer composition.

The magnetically receptive material may be any material that ismagnetically receptive or otherwise capable of induction heating.Indeed, as used herein, the term “magnetically receptive material”refers to any material that is capable of generating eddy currents inthe material in response to an alternating magnetic field. The eddycurrents generated in the magnetically receptive material generate heatwithin the additive which is then dissipated to the polymer matrix,throughout the tool manufactured using the polymer composition, and tothe composite part being cured on the tool. With that in mind, those ofordinary skill in the art would be capable of selecting an appropriatematerial for the magnetically receptive additive based on the polymer inthe polymer composition, and on the desired magnetic and inductionheating properties of the resulting composite tool (e.g., the desiredefficiency, rate or amount of heating). Nonlimiting examples of suitablemagnetically receptive materials include those described in U.S.Provisional Application No. 62/882,423, titled “POLYMER COMPOSITIONSCAPABLE OF INDUCTION HEATING FOR EXTRUSION AND ADDITIVE MANUFACTURINGPROCESSES,” filed on Aug. 2, 2019 in the name of Airtech International,Inc. to which this application claims priority, the entire content ofwhich is incorporated herein by reference, and was attached as AppendixA to U.S. Provisional Application 62/882,425 to which this applicationclaims priority.

The inclusion of a magnetically receptive material in the polymercomposition provides unique “self-heating” properties to themanufactured tool. As used herein, the term “self-heating” referencesthe capability of the manufactured tool to be heated by induction.Details and benefits of this “self-heating” property, as well as systemsand methods of using a manufactured tool having this property are alsodescribed in U.S. Provisional Application No. 62/882,423, titled“POLYMER COMPOSITIONS CAPABLE OF INDUCTION HEATING FOR EXTRUSION ANDADDITIVE MANUFACTURING PROCESSES,” filed on Aug. 2, 2019 in the name ofAirtech International, Inc. to which this application claims priority,the entire content of which is incorporated herein by reference and wasattached as Appendix A to U.S. Provisional Application No. 62/882,425 towhich this application claims priority.

Additionally, the colorant may be any suitable material capable ofimparting the desired color to the additively manufactured or extrudedtool. The addition of colorants to polymer compositions used in additivemanufacturing and extrusion processes is well known to those of ordinaryskill in the art, and any colorants may be used, which materials arealso known to those of ordinary skill in the art. When included in thepolymer composition, a single type of colorant may be used, or acombination of two or more different types of colorants may be used toachieve the desired color, without limitation. Also, the amount of thecolorant(s) in the polymer composition is not particularly limited, andmay be any amount suitable amount to achieve the desired color in theadditively manufactured or extruded tool. As the amount of colorantneeded to achieve the desired color of the additively manufactured orextruded tool may differ depending on the remaining components of thepolymer composition, the amount of colorant may be tailored or selectedbased on the polymer composition and the desired color of themanufactured tool. Those of ordinary skill in the art would be capableof selecting an appropriate amount of an appropriate colorant based onthe composition of the polymer composition and the desired color of themanufactured tool. In some embodiments, for example, the colorant may beincluded in the polymer composition in an amount of about 0.1 to about10 vol % (based on the total volume of the polymer composition).

In embodiments including an auxiliary additive, the polymer compositionmay include a single type of auxiliary additive or a combination of twoor more different types of auxiliary additives. When the polymercomposition includes more than one type of auxiliary additive (e.g.,both a strengthener and a magnetically receptive material, or all threeof a strengthener, magnetically receptive material and colorant), eachof the different auxiliary additives may be independently included inthe polymer composition in an amount of about 1 to about 30 vol % basedon the total volume of the polymer composition (or about 0.1 to about 10vol % for the colorant). Alternatively, in some embodiments, the sumtotal of the amounts of all auxiliary additives in the polymercomposition may be about 1 to about 60 vol % (based on the total volumeof the polymer composition), or about 1 to about 30 vol % (based on thetotal volume of the polymer composition). In embodiments in which thesum total of the different types of auxiliary additives is about 1 toabout 60 vol %, or about 1 to about 30 vol % (based on the total volumeof the polymer composition), the ratio and/or proportions of thedifferent auxiliary additives is not particularly limited. For example,the different auxiliary additives may be included in equal or unequalamounts, which may be tailored as discussed above to achieve the desiredeffect (e.g., the desired, strength, color, “self-heating,” and/orthermal expansion properties).

Additionally, in some embodiments, when the polymer composition includesone or more auxiliary additives, the total amount of all additives inthe polymer composition (e.g., the sum total of the amount of the NTEadditive and all auxiliary additives) may be about 1 to about 60 vol %(based on the total volume of the polymer composition), about 1 to about50 vol % (based on the total volume of the polymer composition), about 1to about 40 vol % (based on the total volume of the polymercomposition), about 1 to about 35 vol % (based on the total volume ofthe polymer composition), or about 1 to about 30 vol % (based on thetotal volume of the polymer composition). As noted above, in embodimentsin which the sum total of the NTE additive and the different types ofauxiliary additives is about 1 to about 60 vol %, about 1 to about 50vol %, about 1 to about 40 vol %, about 1 to about 35 vol %, or about 1to about 30 vol %, the ratio and/or proportions of the NTE additive anddifferent auxiliary additives is not particularly limited. For example,the NTE additive may still be included in an amount within the rangesdiscussed above in connection with the NTE additive, and the NTEadditive and different auxiliary additives may be included in equal orunequal amounts, which may be tailored as discussed above to achieve thedesired effect (e.g., the desired, strength, color, “self-heating,”and/or thermal expansion properties).

The polymer compositions disclosed herein may be made by any suitablemixing or compounding technique, without limitation. Indeed, any mixingor compounding technique currently known in the art or hereafterdeveloped (e.g., known techniques for mixing/compounding thermosets andthermoplastics) may be used to prepare the polymer compositionsdescribed herein. By way of nonlimiting example, for instance, a twinscrew extruder may be used for even mixing of the components at theproper melting temperature and shear rate, which melting temperature andshear rate would be easily discernable by those of ordinary skill in theart based on the polymer used in the polymer composition. As anothernonlimiting example, the components of the polymer composition maysimply be mixed together at the appropriate melting temperature, whichmelting temperature would be easily discernable by those of ordinaryskill in the art based on the polymer used in the polymer composition.

As discussed above, the polymer compositions disclosed herein areconfigured for use in additive manufacturing and extrusion processingtechniques to form cured structures that can serve as molds, cauls,bladders, intensifiers, etc. for the fabrication of composite parts. Thecured structures (e.g., molds, cauls, bladders, intensifiers, etc.) madefrom the additive manufacturing or extrusion processes are configured tobe capable of heating to sufficient temperatures to cure a compositepart composition or laminate. The cured structures may be heated in anysuitable manner, including but not limited to heating the tool and theapplied composite part composition (or laminate) in an oven or autoclaveunder vacuum conditions (e.g., in a vacuum bag), employing heater packs,resistive circuits (e.g., as described in U.S. Patent Publication No.2018/0281279 to Barocio, et al., titled “METHODS AND APPARATUS FOREMBEDDING HEATING CIRCUITS INTO ARTICLES MADE BY ADDITIVE MANUFACTURINGAND ARTICLES MADE THEREFROM,” and filed on Mar. 28, 2018, the entirecontent of which is incorporated herein by reference), channeled fluids,air induction, etc. In some embodiments, the cured structures may beconfigured for induction heating, by, for example, the application of aheating blanket (e.g., as described in U.S. Pat. No. 9,259,886 to Matsenet al., titled “CURING COMPOSITES OUT-OF-AUTOCLAVE USING INDUCTIONHEATING WITH SMART SUSCEPTORS,” and filed on Sep. 29, 2011), the entirecontent of which is incorporated herein by reference), or the inclusionof the magnetically receptive material as an auxiliary additive, asdiscussed above and in more detail in U.S. Provisional Application No.62/882,423, titled “POLYMER COMPOSITIONS CAPABLE OF INDUCTION HEATINGFOR EXTRUSION AND ADDITIVE MANUFACTURING PROCESSES,” filed on Aug. 2,2019 in the name of Airtech International, Inc. to which thisapplication claims priority, the entire content of which is incorporatedherein by reference and was attached as Appendix A to U.S. ProvisionalApplication No. 62/882,425 to which this application claims priority.Regardless of the heating method, however, the heat generated in themanufactured tool transfers to the composite part composition (orlaminate) coated (or placed) on the tool surface, thereby curing thecomposition (or laminate) and completing manufacture of the compositepart.

As discussed herein, the polymer compositions disclosed herein,including the NTE material (and sometimes other auxiliary additives) inthe polymer matrix enable tailoring of the CTE of the cured structures(e.g., molds, cauls, bladders, intensifiers, etc.). Indeed, comparingthe CTE achieved by polymer compositions including varying amounts(i.e., 5 vol %, 10 vol % and 15 vol %) of an example NTE additive (i.e.,zirconium tungstate) in an example polymer system (i.e., ABS) that alsoincludes 20 vol % carbon fibers (as an example auxiliary additive, i.e.,a strengthener), it was found that the CTE of the polymer compositioncould be adjusted from 135 ppm/C (or higher) down to very low levels(e.g., near zero, or below 5 ppm/C) by adjusting the volume percent ofthe NTE material (and leaving the amount of the carbon fibers constant).As can be seen from this comparison, adjusting the amount of the NTEmaterial in the polymer compositions enables tailoring of the CTE of thecomposition, as discussed herein.

As would be appreciated by those of ordinary skill in the art, and asdiscussed generally above, the amount of the NTE needed to accomplish adesired CTE may differ depending on the type of polymer used in thecomposition, and/or on the type and amount of any auxiliary additives inthe composition. Additionally, the amount of the NTE additive may differdepending on the desired CTE of the composite part being manufacturedusing the tool made from the polymer composition. For example, in someembodiments, polymer compositions used to make tools intended for use infabrication fiberglass or aramid based composite parts may require lessof the NTE additive (compared to compositions used to make toolsintended for use in fabricating carbon fiber composite parts) to achievethe desired CTE (i.e., a CTE matched or generally matched to the desiredCTE of the composite part). And in some embodiments, polymercompositions used to make tools intended for use in fabricating aramidbased composite parts may require more of the NTE additive (compared tocompositions used to make tools intended for use in fabricatingfiberglass based composite parts) to achieve the desired CTE match.

For instance, in some embodiments in which the composite part beingfabricating is aramid based, the polymer composition used to make thetool for fabricating the aramid based composite part may include about15 to about 40 vol % of the NTE additive, or about 20 to about 30 vol %,or about 25 to about 30 vol %, based on 100 vol % of the polymercomposition. In addition, the NTE additive may be included at any valuewithin any of these ranges, and within any sub-range within theseranges, without limitation. For example, the NTE additive may beincluded in an amount of about 15 vol %, 18, vol %, 20 vol %, 24 vol %,28 vol %, 30 vol %, 34 vol %, 38 vol % or 40 vol % based on 100 vol % ofthe polymer composition.

Also, in some embodiments in which the composite part being fabricatingis fiberglass based, the polymer composition used to make the tool forfabricating the fiberglass based composite part may include about 10 toabout 30 vol % of the NTE additive, or about 10 to about 25 vol %, orabout 15 to about 25 vol %, or about 15 to about 20 vol %, based on 100vol % of the polymer composition. In addition, the NTE additive may beincluded at any value within any of these ranges, and within anysub-range within these ranges, without limitation. For example, the NTEadditive may be included in an amount of about 10 vol %, 12 vol %, 14vol %, 16 vol %, 18 vol %, 20 vol %, 22 vol %, 24 vol %, 26 vol %, 28vol % or 30 vol %, based on 100 vol % of the polymer composition.

And in some embodiments in which the composite part being fabricating iscarbon fiber based, the polymer composition used to make the tool forfabricating the carbon fiber based composite part may include about 20to about 60 vol % of the NTE additive, or about 20 to about 50 vol %, orabout 30 to about 50 vol %, or about 35 to about 45 vol %, based on 100vol % of the polymer composition. In addition, the NTE additive may beincluded at any value within any of these ranges, and within anysub-range within these ranges, without limitation. For example, the NTEadditive may be included in an amount of about 20 vol %, 25 vol %, 30vol %, 35 vol %, 40 vol %, 45 vol %, 50 vol %, 55 vol % or 60 vol %,based on 100 vol % of the polymer composition.

In some embodiments, a method of fabricating a tool (e.g., a mold, caul,bladder, intensifier, etc.) includes forming the tool by additivemanufacturing or extrusion using the polymer composition according toembodiments of the present disclosure. The method may further includefirst preparing the polymer composition including the NTE additive byany suitable technique, as discussed above. The additive manufacturingand extrusion processes for forming the tool are not particularlylimited and may include any known or hereafter developed additivemanufacturing and extrusion techniques. For example, in some embodimentsthe additive manufacturing technique may include extrusion, 3D printing,fused deposition modeling, fused filament fabrication, powder bedfusion, molten polymer deposition, photopolymerization, directed energydeposition, sheet lamination, material jetting or binder jetting, etc.In some embodiments, and where necessary based on the manufacturingtechnique employed to additively manufacture or extrude the tool, themethod may further include curing the polymer composition afterextrusion or additive manufacturing.

As would be understood by those of ordinary skill in the art, extrusionand additive manufacturing processes create a three-dimensional objectby layer-after-layer deposition of the “printing” composition. Thepolymer compositions discussed herein may be used as the “printing”compositions in any of these extrusion and additive manufacturingprocesses. For example, as shown generally (and by way of example only,without limitation) in FIGS. 1 and 1A, an extruder 10 (or other additivemanufacturing device) extrudes multiple layers 12 of the molten polymercomposition through the extruder nozzle 14. The extruder 10 continuesforming layers 12 of the polymer composition on top of each other untilthe object is complete. According to embodiments of the presentdisclosure, the layers 12 of the polymer compositions include NTEmaterials 16 embedded in the polymer matrix 22. And in some embodiments,the polymer compositions also include embedded fiber additives 18 (e.g.,carbon fibers or other additives), and optionally, additional auxiliaryadditives 20 (e.g., colorants, etc.). In the layers depicted in theexploded view of FIG. 1A, the NTE materials 16, fiber additives 18(e.g., carbon fibers) and other auxiliary additives 20 are embeddedrandomly in the extruded layers 12 of the composition. Indeed, as shownin FIG. 1A, the NTE materials 16 and auxiliary additives 18 aregenerally uniformly dispersed within the layers 12.

In some embodiments, the tool manufacturing process may varysignificantly when the polymer composition includes a thermoset polymerversus a thermoplastic polymer. For example, when the polymercomposition is prepared by a chemical curing mechanism (e.g., when thepolymer matrix includes a thermoset polymer), the NTE additive and anyauxiliary additives may be mixed into the polymer composition in anysuitable manner, e.g., by either mixing them into the monomer mixture orinto the hardener (or curing agent) before mixing the two components(i.e., the monomer mixture and hardener component) together and printingthe polymer composition. The separate components of the polymer mixture(i.e., the monomer mixture and the hardener component) can be combinedin any suitable manner using any suitable equipment, such as but notlimited to using a static mixer, or mixing by hand (e.g., usingavailable scales and mixing equipment). Methods of mixing the separatepolymer composition components are well known to those of ordinary skillin the art, and those ordinary artisans would be capable of selecting anappropriate mixing technique based on the selected components of thepolymer composition. The separate components of the polymer composition(i.e., the monomer component which may include all or a portion of theadditives, and the hardener component which may include all or a portionof the additives) may then be combined to form the polymer compositionusing any known or suitable mixing or combination technique. In someembodiments, however, the monomer component, additives and hardenercomponent are all mixed together by any suitable technique to form aself-contained polymer composition.

In some embodiments, the polymer composition (i.e., either the combinedmonomer component and hardener component, or the self-contained polymercomposition) may be pre-heated to prepare the composition for furtherprocessing. Once mixed and/or pre-heated, the polymer composition may bepumped to the printing component of the selected additive manufacturingequipment (e.g., a print head) in the mixed state, thereby enabling thecomposition to be printed. Additionally, when a thermoset polymer isused as the polymer matrix, and when the polymer composition includesthe magnetically receptive material as an auxiliary additive, the mixedand/or pre-heated polymer composition can be cured (or partially cured)concurrently with printing by exposure to induction heating at theprinting component (e.g., the print head). More specifically, exposingthe polymer composition to the induction heating at the printingcomponent elevates the temperature of the polymer composition, therebyadvancing the curing reaction without the need for highly exothermiccuring reactions. Indeed, conventional methods of additive manufacturingrely on highly exothermic reactions to quickly advance the cross-linkingin the polymer and cure the bead to a point sufficient to allow anotherlayer to be deposited on top of the bead. However, according toembodiments of the present disclosure including the magneticallyreceptive material in the polymer composition, the bead can be morerapidly cured by induction heating, which allows different resin systemsto be used (which don't rely on highly exothermic reactions for cure).This broadly extends the range of thermosets that can be used withadditive manufacturing.

As generally noted above, the polymer compositions disclosed herein areadditively manufactured or extruded to form a tool or cured structure(e.g., a mold, caul, bladder, intensifier, etc.). This tool may be usedto fabricate composite parts for various different purposes (e.g., themanufacture of composite parts for the aerospace industry). According tosome embodiments, the tool includes a cured polymer matrix with NTEparticles (or fibers) dispersed throughout the matrix. The cured polymermatrix with the dispersed NTE particles (or fibers) is prepared byadditive manufacturing or extrusion techniques using the polymercompositions disclosed herein. Therefore, the cured polymer matrix isthe cured form of the polymer matrix materials discussed above inconnection with the polymer compositions. Similarly, the NTE particles(or fibers) are the particles (or fibers) of the NTE additive (alsodescribed above) that become dispersed throughout the polymer matrixduring the additive manufacturing or extrusion process. As would beunderstood by those skilled in the art, the amount of the NTE particles(or fibers) in the cured polymer matrix (relative to the amount of thepolymer) can be calculated from the above described volume percentagesof the NTE additive and the polymer materials in the polymer compositionusing the densities and molecular weights of the polymer and additivematerials.

The tool may have any desired shape or structure. Indeed, one of theadvantages of using an additive manufacturing technique is the abilityto generate complex tool structures. In some embodiments, however, thetool has a substantially or generally constant shape, including asubstantially or generally constant cross-sectional shape throughout thetool. Tools having such a constant cross-sectional shape may bemanufactured by extrusion techniques and may be used for variouspurposes, such as, but not limited to seals, intensifiers, internallymolded components, etc. In some embodiments, the tools (e.g., molds,cauls, mandrels, bladders, etc.) may be manufactured by an additivemanufacturing technique to have more complex structures, such as, butnot limited to net shapes. Additionally or alternatively, the shapesachieved by either the additive manufacturing technique or the extrusiontechnique can be further processed (after the additive manufacturing orextrusion), e.g., by machining, to form more complex final shapes.

According to some embodiments, a method of manufacturing a compositepart includes coating, placing or otherwise applying a composite partcomposition or laminate on or to a tool (e.g., a mold, caul, bladder,intensifier, etc.), and exposing the tool to heat sufficient to cure thecomposite part composition or laminate. The tool may be any of the toolsadditively manufactured or extruded from the polymer compositions, asdescribed herein. The composite part composition or laminate is notparticularly limited, and may have any suitable composition andstructure. Indeed, compositions and structures (e.g., laminatestructures) for composite parts are well known in the industry, andthose of ordinary skill in the art would be capable of selecting anappropriate composite part composition or laminate structure based onthe desired structure of the cured composite part and the intendedapplication or use for the composite part.

As discussed above, the tool may be heated in any suitable manner (e.g.,in an oven or autoclave under vacuum conditions, with heater packs,resistive circuits, etc.). In embodiments in which the polymercomposition includes the magnetically receptive material as an auxiliaryadditive, however, exposing the tool to heat may include exposing thetool to an alternating magnetic field to induce eddy currents in themagnetically receptive material. This method, as well as systems andmethods for controlling the amount of heat generated in the magneticallyreceptive material are described in detail in U.S. ProvisionalApplication No. 62/882,423 titled “POLYMER COMPOSITIONS CAPABLE OFINDUCTION HEATING FOR EXTRUSION AND ADDITIVE MANUFACTURING PROCESSES,”filed on Aug. 2, 2019 in the name of Airtech International, Inc. towhich this application claims priority, the entire content of which isincorporated herein by reference and was attached hereto as Appendix Ato U.S. Provisional Application No. 62/882,425 to which this applicationclaims priority.

According to some embodiments of the present disclosure, as shown inFIG. 1 , a system 100 for manufacturing a composite part includes a tool110 (e.g., a mold, caul, bladder, intensifier, etc.), a heating element120, and a controller 130 (e.g., a PID controller) for cycling theheating element 120 on and off. The tool 110 is the additivelymanufactured or extruded tool including NTE particles (or fibers) 112dispersed throughout a cured polymer matrix 114 of the tool structure.The heating element 120 may be any suitable heating element capable ofthe tool 110 to a temperature sufficient to cure the compositecomposition or laminate applied to the surface of the tool. For example,in some embodiments, the heating element 120 may be an oven, auto-clave,heating blanket, etc. In embodiments in which the tool 110 includesmagnetically receptive particles (or fibers or wires), the heatingelement 120 may be replaced with a magnetic field generator, asdiscussed in detail in U.S. Provisional Application No. 62/882,423titled “POLYMER COMPOSITIONS CAPABLE OF INDUCTION HEATING FOR EXTRUSIONAND ADDITIVE MANUFACTURING PROCESSES,” filed on Aug. 2, 2019 in the nameof Airtech International, Inc. to which this application claimspriority, the entire content of which is incorporated herein byreference and was attached hereto as Appendix A to U.S. ProvisionalApplication No. 62/882,425 to which this application claims priority.

The controller 130 may be any suitable controller (for example a PIDcontroller) capable of cycling or switching the heating element 120 onand off. In some embodiments, the system 100 may also include one ormore thermocouples 140 in contact with, permanently connected to, orembedded within the tool 110. The thermocouples 140 are also incommunication with the controller 130. The thermocouples 140 togetherwith the controller 130 may define a continuous feedback loop thatcontinuously detects the temperature of the tool 110 at regularintervals (using the thermocouples 140), and automatically cycles theheating element 120 on or off in response to the temperature data fromthe thermocouples (using the controller) when the temperature of thetool reaches or exceeds a predetermined threshold temperature. Thepredetermined threshold temperature is not particularly limited, and maybe any temperature suitable to prevent the tool from melting or failingin response to excess heat generation. For example, the predeterminedthreshold temperature may be set at the Tg, softening or melting pointof the polymer matrix. However, in some embodiments, the predeterminedthreshold temperature is set at a temperature below the Tg, softening ormelting point of the polymer in order to prevent tool failure. Forexample, in some embodiments, the predetermined threshold temperature isset at least 10° C., at least 20° C., at least 30° C., or at least 50°C. below the Tg, softening or melting point of the polymer.

Although various embodiments of the disclosure have been described,additional modifications and variations will be apparent to thoseskilled in the art. For example, the compositions may have additionalcomponents, which may be present in various suitable amounts, forexample, other additives suitable to improve and/or modify theproperties of the polymer compositions or resulting tools. Similarly,the methods of preparing the polymer compositions, tools or compositeparts as described herein by way of example embodiments may be modifiedin accordance with the knowledge in the field to which the variousembodiments pertain. For example, the methods may include additionalactions or steps, may be performed at various temperatures and speeds,and/or may be otherwise suitably modified (e.g., as described withreference to the polymer compositions). As such, the disclosure is notlimited to the embodiments specifically disclosed, and the compositions,systems and methods may be modified without departing from thedisclosure.

Throughout the text and claims, any use of the word “about” reflects thepenumbra of variation associated with measurement, significant figures,and interchangeability, all as understood by a person having ordinaryskill in the art to which this disclosure pertains. Further, when usedherein, the terms “substantially” and “generally” are used as terms ofapproximation and not as terms of degree, and are intended to accountfor normal variations and deviations in the measurement or assessmentassociated with the compositions, systems, and methods (e.g., in thedescription of physical or chemical properties of various components orcompositions and in the description of amounts of various components).

What is claimed is:
 1. A method of making a composite part, the methodcomprising: additively manufacturing or extruding a polymer compositionto form a tool, the polymer composition comprising a polymer matrix anda negative thermal expansion (NTE) additive, and a volume of the NTEadditive in the polymer composition being configured to yield the toolhaving a first coefficient of thermal expansion (CTE); applying acomposite part composition or composite part laminate on or to the tool,the composite part composition or composite part laminate beingconfigured to yield the composite part having a second CTE that isgenerally matched to the first CTE of the tool; and exposing the tool tosufficient heat to cure the composite part composition or composite partlaminate to yield the composite part having the second CTE that isgenerally matched to the first CTE of the tool.
 2. The method of claim1, wherein the NTE additive comprises a powder or particulate having anaverage particle size of about 10 μm or smaller.
 3. The method of claim1, wherein the NTE additive comprises a material selected from the groupconsisting of: transition metal tungstates; transition metal molybdates;zirconium vanadates; zeolites exhibiting NTE; aluminum phosphatesexhibiting NTE; Prussian blue analogs; antiperovskite manganesenitrides; β-eucryptite; BiNi_(1−x)Fe_(x)O₃ compounds in which x is lessthan 1 and greater than 0; Ca₂RuO_(4−γ); combinations thereof, hybridsthereof, and mixtures thereof.
 4. The method of claim 1, wherein thepolymer composition further comprises one or more auxiliary additives.5. The method of claim 4, wherein the one or more auxiliary additivescomprises one or more strengtheners, one or more magnetically receptivematerials, or one or more colorants.
 6. The method of claim 5, whereinthe one or more strengtheners comprises a material selected from thegroup consisting of carbon fibers, glass fibers, aramid fibers, metalfibers, metal coated fibers, and combinations thereof.
 7. The method ofclaim 1, wherein the NTE additive is present in the polymer compositionin an amount of about 1 to about 60 vol % based on 100 vol % of thepolymer composition.
 8. The method of claim 1, wherein the additivelymanufacturing or extruding the polymer composition comprises extrudingthe polymer composition to form the tool, and the tool has a constantcross-section.
 9. The method of claim 1, wherein the additivelymanufacturing or extruding the polymer composition comprises additivelymanufacturing the polymer composition to form the tool, and the toolcomprises a net shape.
 10. The method according to claim 4, wherein theNTE additive and the auxiliary additives are present in the polymercomposition in a sum total amount of about 1 to about 60 vol % based on100 vol % of the polymer composition.
 11. The method according to claim1, wherein the NTE additive comprises an NTE material coated with acoating material.
 12. A method of making a composite part, the methodcomprising: additively manufacturing or extruding a polymer compositionto form a tool, the polymer composition comprising a polymer matrix, oneor more strengtheners, and a negative thermal expansion (NTE) additive,and a volume of the NTE additive in the polymer composition beingconfigured to yield the tool having a first coefficient of thermalexpansion (CTE); applying a composite part composition or composite partlaminate on or to the tool, the composite part composition or compositepart laminate configured to yield the composite part having a second CTEthat is generally matched to the first CTE of the tool; and exposing thetool to sufficient heat to cure the composite part composition orcomposite part laminate to yield the composite part having the secondCTE that is generally matched to the first CTE of the tool.
 13. Themethod of claim 12, wherein the NTE additive comprises a powder orparticulate having an average particle size of about 10 μm or smaller.14. The method of claim 12, wherein the NTE additive comprises amaterial selected from the group consisting of: transition metaltungstates; transition metal molybdates; zirconium vanadates; zeolitesexhibiting NTE; aluminum phosphates exhibiting NTE; Prussian blueanalogs; antiperovskite manganese nitrides; β-eucryptite;BiNi_(1−x)Fe_(x)O₃ compounds in which x is less than 1 and greater than0; Ca₂RuO_(4−γ); combinations thereof, hybrids thereof, and mixturesthereof.
 15. The method of claim 12, wherein the one or morestrengtheners comprises a material selected from the group consisting ofcarbon fibers, glass fibers, aramid fibers, metal fibers, metal coatedfibers, and combinations thereof.
 16. The method of claim 12, whereinthe NTE additive is present in the polymer composition in an amount ofabout 1 to about 60 vol % based on 100 vol % of the polymer composition.17. The method of claim 12, wherein the additively manufacturing orextruding the polymer composition comprises extruding the polymercomposition to form the tool, and the tool has a constant cross-section.18. The method of claim 12, wherein the additively manufacturing orextruding the polymer composition comprises additively manufacturing thepolymer composition to form the tool, and the tool comprises a netshape.
 19. The method of claim 12, wherein the NTE additive and the oneor more strengtheners are present in the polymer composition in a sumtotal amount of about 1 to about 60 vol % based on 100 vol % of thepolymer composition.
 20. The method of claim 12, wherein the NTEadditive comprises an NTE material coated with a coating material.